INDEX TO VOLCANIC ISLANDS.Abel, M., on calcareous casts at the Cape of Good Hope261Abingdon island234Abrolhos islands, incrustation on188Aeriform explosions at Ascension191Albatross, driven from St. Helena225Albemarle island234Albite, at the Galapagos archipelago234Amygdaloidal cells, half filled184Amygdaloids, calcareous origin of176Ascension, arborescent incrustation on rocks of188—— absence of dikes, freedom from volcanic action, and state of lava-streams226Ascidia, extinction of258Atlantic Ocean, new volcanic focus in226Augite, fused239Australia251Azores182,248Bahia in Brazil, dikes at247Bailly, M., on the mountains of Mauritius185Bald Head260Banks’ Cove234,236Barn, The, St. Helena216Basalt, specific gravity of245Basaltic coast-mountains at Mauritiu185—— at St. Helena218—— at St. Jago178Beaumont, M. Elie de, on circular subsidences in lava233—— on dikes indicating elevation228—— on inclination of lava-streams227—— on laminated dikes212Bermuda, calcareous rocks of260,262Beudant, M., on bombs191—— on jasper197—— on laminated trachyte211—— on obsidian of Hungary207—— on silex in trachyte270,197Bole257Bombs, volcanic189Bory St. Vincent, on bombs190Boulders, absence in Australia and Cape of Good Hope265Brattle island238Brewster, Sir D., on a calcareo-animal substance201—— on decomposed glass252Brown, Mr. R., on extinct plants from Van Diemen’s land257—— on sphærulitic bodies in silicified wood207Buch, Von, on cavernous lava233—— on central volcanoes249—— on crystals sinking in obsidian243—— on laminated lava209—— on obsidian streams208—— on olivine in basalt234—— on superficial calcareous beds in the Canary islands224Calcareous deposit at St. Jago affected by heat169,171—— fibrous matter, entangled in streaks in scoriæ174—— freestone at Ascension198—— incrustations at Ascension199—— sandstone at St. Helena222—— superficial beds at King George’s sound260Cape of Good Hope263Carbonic acid, expulsion of, by heat171,176Carmichael, Capt., on glassy coatings to dikes216Casts, calcareous, of branches261Chalcedonic nodules257Chalcedony in basalt and in silicified wood196Chatham island231,235,241,248,259Chlorophæite257Clarke, Rev. W., on the Cape of Good Hope258,263Clay-slate, its decomposition and junction with granite at the Cape of Good Hope264Cleavage of clay-slate in Australia252Cleavage, cross, in sandstone253Coast denudation at St. Helena226Columnar basalt173“Comptes Rendus,” account of volcanic phenomena in the Atlantic226Concepcion, earthquake of228,249Concretions in aqueous and igneous rocks compared206—— in tuff197—— of obsidian206,208Conglomerate, recent, at St. Jago181Coquimbo, curious rock of261Corals, fossil, from Van Diemen’s Land256Crater, segment of, at the Galapagos238—— great central one at St. Helena219—— internal ledges round, and parapet on220Craters, basaltic, at Ascension189—— form of, affected by the trade wind189—— of elevation227—— of tuff at Terceira182—— of tuff at the Galapagos archipelago230,231,235,237—— their breached state240—— small basaltic at St. Jago177—— —— at the Galapagos archipelago232Crystallisation favoured by space211Dartigues, M., on sphærulites207Daubeny, Dr., on a basin-formed island237—— on fragments in trachyte193D’Aubuisson on hills of phonolite222—— on the composition of obsidian206—— on the lamination of clay-slate210De la Beche, Sir H., on magnesia in erupted lime174—— on specific gravity of limestones198Denudation of coast at St. Helena226Diana’s Peak, St. Helena220Dieffenbach, Dr., on the Chatham Islands259Dikes, truncated, on central crateriform ridge of St. Helena219—— at St. Helena; number of; coated by a glossy layer; uniform thickness of216—— great parallel ones at St. Helena222—— not observed at Ascension226—— of tuff231—— of trap in the plutonic series247—— remnants of, extending far into the sea round St. Helena226Dislocations at Ascension192—— at St. Helena217,221Distribution of volcanic islands248Dolomieu, on decomposed trachyte182—— on laminated lava210,211—— on obsidian208Drée, M., on crystals sinking in lava243Dufrenoy, M., on the composition of the surface of certain lava-streams209,243—— on the inclination of tuff-strata236Eggs of birds embedded at St. Helena224—— of turtle at Ascension198Ejected fragments at Ascension192—— at the Galapagos archipelago239Elevation of St. Helena225—— the Galapagos archipelago241—— Van Diemen’s Land, Cape of Good Hope, New Zealand, Australia, and Chatham island258—— of volcanic islands250Ellis, Rev. W., on ledges within the great crater at Hawaii220—— on marine remains at Otaheite184Eruption, fissures of224,249,250Extinction of land-shells at St. Helena224Faraday, Mr., on the expulsion of carbonic acid gas171Feldspar, fusibility of246—— in radiating crystals263—— Labrador, ejected193Feldspathic lavas179—— at St. Helena219—— rock, alternating with obsidian202—— lamination, and origin of209Fernando Noronha181,210Ferruginous superficial beds259Fibrous calcareous matter at St. Jago174Fissures of eruption242,249,250Fitton, Dr., on calcareous breccia262Flagstaff Hill, St. Helena216Fleurian de Bellevue on sphærulites207Fluidity of lavas234,235Forbes, Professor, on the structure of glaciers212Fragments ejected at Ascension192—— at the Galapagos archipelago239Freshwater Bay238,243Fuerteventura (Feurteventura), calcareous beds of224Galapagos archipelago229—— parapets round craters220Gay Lussac, on the expulsion of carbonic acid gas171Glaciers, their structure212Glossiness of texture, origin of206Gneiss, derived from clay-slate264—— with a great embedded fragment252Gneiss-granite, form of hills of259Good Hope, Cape of263Gorges, narrow, at St. Helena225Granite, junction with clay-slate, at the Cape of Good Hope263Granitic ejected fragments192,239Gravity, specific, of lavas243-8Gypsum, at Ascension201—— in volcanic strata at St. Helena215—— on surface of the ground at ditto223Hall, Sir J., on the expulsion of carbonic acid gas171Heat, action of, on calcareous matter170Hennah, Mr., on ashes at Ascension189Henslow, Prof., on chalcedony197Hoffmann, on decomposed trachyte182Holland, Dr., on Iceland228Horner, Mr., on a calcareo-animal substance201—— on fusibility of feldspar246Hubbard, Dr., on dikes247Humboldt on ejected fragments193—— on obsidian formations207,209—— on parapets round craters220—— on sphærulites210Hutton on amygdaloids176Hyalite in decomposed trachyte182Iceland, stratification of the circumferential hills228Islands, volcanic, distribution of248—— their elevation250Incrustation, on St. Paul’s rocks187Incrustations, calcareous, at Ascension199Jago, St.167James island234,237,242Jasper, origin of196Jonnès, M. Moreau de, on craters affected by wind189Juan Fernandez250Keilhau, M., on granite264Kicker Rock232King George’s sound259Labrador feldspar, ejected193Lakes at bases of volcanoes229Lamination of volcanic rocks209Land-shells, extinct, at St. Helena224Lanzarote, calcareous beds of223Lava, adhesion to sides of a gorge177—— feldspathic179—— with cells semi-amygdaloidal184Lavas, specific gravity of243,247Lava-streams blending together at St. Jago177—— composition of surface of208—— differences in the state of their surfaces244—— extreme thinness of238—— heaved up into hillocks at the Galapagos archipelago233—— their fluidity234,235—— with irregular hummocks at Ascension189Lead, separation from silver244Lesson, M., on craters at Ascension189Leucite234Lime, sulphate of, at Ascension200Lonsdale, Mr., on fossil-corals from Van Diemen’s land256Lot, St. Helena221Lyell, Mr., on craters of elevation227—— on embedded turtles’ eggs198—— on glossy coating to dikes216Macaulay, Dr., on calcareous casts at Madeira262MacCulloch, Dr., on an amygdaloid184—— on chlorophæite287—— on laminated pitchstone209Mackenzie, Sir G., on cavernous lava-streams233—— on glossy coatings to dikes216—— on obsidian streams208—— on stratification in Iceland228Madeira, calcareous casts at262Magazine, Nautical,—account of volcanic phenomena in the Atlantic226Marekanite206Mauritius, crater of elevation of184,227Mica, in rounded nodules168—— origin in metamorphic slate264—— radiating form of263Miller, Prof., on ejected Labrador feldspar193—— on quartz crystals in obsidian beds202Mitchell, Sir T., on bombs191—— on the Australian valleys254Mud streams at the Galapagos archipelago236Narborough island234Nelson, Lieut., on the Bermuda islands260,262New Caledonia248New Red sandstone, cross cleavage of253New South Wales251New Zealand259Nulliporæ (fossil), resembling concretions169Obsidian, absent at the Galapagos archipelago241—— bombs of191—— composition and origin of207,208—— crystals of feldspar sink in243—— its irruption from lofty craters246—— passage of beds into202—— specific gravity of243,246—— streams of208Olivine decomposed at St. Jago178—— at Van Diemen’s land257—— in the lavas at the Galapagos archipelago234Oolitic structure of recent calcareous beds at St. Helena223Otaheite183Oysters, extinction of258Panza islands, laminated trachyte of209Pattinson, Mr., on the separation of lead and silver244Paul’s, St., rocks of187Pearlstone206Peperino232Péron, M., on calcareous rocks of Australia262,263Phonolite, hills of179,181,221—— laminated210—— with more fusible hornblende246Pitchstone204—— dikes of209Plants, extinct257Plutonic rocks, separation of constituent parts of, by gravity246Porto Praya167Prevost, M. C., on rarity of great dislocations in volcanic islands217Prosperous hill, St. Helena218Pumice, absent at the Galapagos archipelago241—— laminated209,210,211Puy de Dome, trachyte of193Quail island, St. Jago168,170,173Quartz, crystals of, in beds alternating with obsidian202—— crystallised in sandstone252—— fusibility of246—— rock, mottled from metamorphic action with earthy matter170Red hill173Resin-like altered scoriæ171Rio de Janeiro, gneiss of252Robert, M., on strata of Iceland228Rogers, Professor, on curved lines of elevation249Salses, compared with tuff craters240Salt deposited by the sea200—— in volcanic strata201,215—— lakes of, in craters240Sandstone of Brazil265—— of the Cape of Good Hope265—— platforms of, in New South Wales252,265Schorl, radiating263Scrope, Mr. P., on laminated trachyte209,210,212—— on obsidian208—— on separation of trachyte and basalt244—— on silex in trachyte176—— on sphærulites210Seale, Mr., geognosy of St. Helena215—— on dikes226—— on embedded birds’ bones225Seale, on extinct shells of St. Helena224Sedgwick, Professor, on concretions206Septaria, in concretions in tuff198Serpulæ on upraised rocks185Seychelles248Shells, colour of, affected by light201—— from Van Diemen’s land256—— land, extinct, at St. Helena224—— particles of, drifted by the wind at St. Helena223Shelly matter deposited by the waves200Siau, M., on ripples254Signal Post Hill168,175,176Silica, deposited by steam182—— large proportion of, in obsidian206,208—— specific gravity of246Siliceous sinter196Smith, Dr. A., on junction of granite and clay-slate264Spallanzani on decomposed trachyte182Specific gravity of recent calcareous rocks and of limestone198—— of lavas245Sphærulites in glass and in silicified wood207—— in obsidian204,210Sowerby, Mr. G. B., on fossil-shells from Van Diemen’s land256—— from St. Jago169—— land-shells from St. Helena224St. Helena214—— crater of elevation of227St. Jago, crater of elevation of227—— effects of calcareous matter on lava231St. Paul’s rocks187,248Stokes, Mr., collections of sphærulites and of obsidians207,212Stony-top, Little218,222—— Great218Stratification of sandstone in New South Wales253,255Streams of obsidian208Stutchbury, Mr., on marine remains at Otaheite184Subsided space at Ascension192Tahiti183Talus, stratified, within tuff craters236Terceira182Tertiary deposit of St. Jago169Trachyte, absent at the Galapagos archipelago241—— at Ascension193—— at Terceira182—— decomposition of, by steam182—— its lamination200,210—— its separation from basalt244—— softened at Ascension194—— specific gravity of245—— with singular veins195Trap-dikes in the plutonic series247—— at King George’s sound259Travertin at Van Diemen’s land257Tropic-bird, now rare, at St. Helena225Tuff, craters of231,235,236—— their breached state240—— peculiar kind of231Turner, Mr., on the separation of molten metals244Tyerman and Bennett on marine remains at Huaheine184Valleys, gorge-like, at St. Helena225—— in New South Wales254—— in St. Jago180Van Diemen’s land256Veins in trachyte195—— of jasper195Vincent, Bory St., on bombs190Volcanic bombs189—— island in process of formation in the Atlantic226—— islands, their distribution248Wacke, its passage into lava183,257Wackes, argillaceous168,178Webster, Dr., on a basin-formed island237—— on gypsum at Ascension201White, Martin, on soundings254Wind, effects of, on the form of craters
Abel, M., on calcareous casts at the Cape of Good Hope261Abingdon island234Abrolhos islands, incrustation on188Aeriform explosions at Ascension191Albatross, driven from St. Helena225Albemarle island234Albite, at the Galapagos archipelago234Amygdaloidal cells, half filled184Amygdaloids, calcareous origin of176Ascension, arborescent incrustation on rocks of188—— absence of dikes, freedom from volcanic action, and state of lava-streams226Ascidia, extinction of258Atlantic Ocean, new volcanic focus in226Augite, fused239Australia251Azores182,248Bahia in Brazil, dikes at247Bailly, M., on the mountains of Mauritius185Bald Head260Banks’ Cove234,236Barn, The, St. Helena216Basalt, specific gravity of245Basaltic coast-mountains at Mauritiu185—— at St. Helena218—— at St. Jago178Beaumont, M. Elie de, on circular subsidences in lava233—— on dikes indicating elevation228—— on inclination of lava-streams227—— on laminated dikes212Bermuda, calcareous rocks of260,262Beudant, M., on bombs191—— on jasper197—— on laminated trachyte211—— on obsidian of Hungary207—— on silex in trachyte270,197Bole257Bombs, volcanic189Bory St. Vincent, on bombs190Boulders, absence in Australia and Cape of Good Hope265Brattle island238Brewster, Sir D., on a calcareo-animal substance201—— on decomposed glass252Brown, Mr. R., on extinct plants from Van Diemen’s land257—— on sphærulitic bodies in silicified wood207Buch, Von, on cavernous lava233—— on central volcanoes249—— on crystals sinking in obsidian243—— on laminated lava209—— on obsidian streams208—— on olivine in basalt234—— on superficial calcareous beds in the Canary islands224Calcareous deposit at St. Jago affected by heat169,171—— fibrous matter, entangled in streaks in scoriæ174—— freestone at Ascension198—— incrustations at Ascension199—— sandstone at St. Helena222—— superficial beds at King George’s sound260Cape of Good Hope263Carbonic acid, expulsion of, by heat171,176Carmichael, Capt., on glassy coatings to dikes216Casts, calcareous, of branches261Chalcedonic nodules257Chalcedony in basalt and in silicified wood196Chatham island231,235,241,248,259Chlorophæite257Clarke, Rev. W., on the Cape of Good Hope258,263Clay-slate, its decomposition and junction with granite at the Cape of Good Hope264Cleavage of clay-slate in Australia252Cleavage, cross, in sandstone253Coast denudation at St. Helena226Columnar basalt173“Comptes Rendus,” account of volcanic phenomena in the Atlantic226Concepcion, earthquake of228,249Concretions in aqueous and igneous rocks compared206—— in tuff197—— of obsidian206,208Conglomerate, recent, at St. Jago181Coquimbo, curious rock of261Corals, fossil, from Van Diemen’s Land256Crater, segment of, at the Galapagos238—— great central one at St. Helena219—— internal ledges round, and parapet on220Craters, basaltic, at Ascension189—— form of, affected by the trade wind189—— of elevation227—— of tuff at Terceira182—— of tuff at the Galapagos archipelago230,231,235,237—— their breached state240—— small basaltic at St. Jago177—— —— at the Galapagos archipelago232Crystallisation favoured by space211Dartigues, M., on sphærulites207Daubeny, Dr., on a basin-formed island237—— on fragments in trachyte193D’Aubuisson on hills of phonolite222—— on the composition of obsidian206—— on the lamination of clay-slate210De la Beche, Sir H., on magnesia in erupted lime174—— on specific gravity of limestones198Denudation of coast at St. Helena226Diana’s Peak, St. Helena220Dieffenbach, Dr., on the Chatham Islands259Dikes, truncated, on central crateriform ridge of St. Helena219—— at St. Helena; number of; coated by a glossy layer; uniform thickness of216—— great parallel ones at St. Helena222—— not observed at Ascension226—— of tuff231—— of trap in the plutonic series247—— remnants of, extending far into the sea round St. Helena226Dislocations at Ascension192—— at St. Helena217,221Distribution of volcanic islands248Dolomieu, on decomposed trachyte182—— on laminated lava210,211—— on obsidian208Drée, M., on crystals sinking in lava243Dufrenoy, M., on the composition of the surface of certain lava-streams209,243—— on the inclination of tuff-strata236Eggs of birds embedded at St. Helena224—— of turtle at Ascension198Ejected fragments at Ascension192—— at the Galapagos archipelago239Elevation of St. Helena225—— the Galapagos archipelago241—— Van Diemen’s Land, Cape of Good Hope, New Zealand, Australia, and Chatham island258—— of volcanic islands250Ellis, Rev. W., on ledges within the great crater at Hawaii220—— on marine remains at Otaheite184Eruption, fissures of224,249,250Extinction of land-shells at St. Helena224Faraday, Mr., on the expulsion of carbonic acid gas171Feldspar, fusibility of246—— in radiating crystals263—— Labrador, ejected193Feldspathic lavas179—— at St. Helena219—— rock, alternating with obsidian202—— lamination, and origin of209Fernando Noronha181,210Ferruginous superficial beds259Fibrous calcareous matter at St. Jago174Fissures of eruption242,249,250Fitton, Dr., on calcareous breccia262Flagstaff Hill, St. Helena216Fleurian de Bellevue on sphærulites207Fluidity of lavas234,235Forbes, Professor, on the structure of glaciers212Fragments ejected at Ascension192—— at the Galapagos archipelago239Freshwater Bay238,243Fuerteventura (Feurteventura), calcareous beds of224Galapagos archipelago229—— parapets round craters220Gay Lussac, on the expulsion of carbonic acid gas171Glaciers, their structure212Glossiness of texture, origin of206Gneiss, derived from clay-slate264—— with a great embedded fragment252Gneiss-granite, form of hills of259Good Hope, Cape of263Gorges, narrow, at St. Helena225Granite, junction with clay-slate, at the Cape of Good Hope263Granitic ejected fragments192,239Gravity, specific, of lavas243-8Gypsum, at Ascension201—— in volcanic strata at St. Helena215—— on surface of the ground at ditto223Hall, Sir J., on the expulsion of carbonic acid gas171Heat, action of, on calcareous matter170Hennah, Mr., on ashes at Ascension189Henslow, Prof., on chalcedony197Hoffmann, on decomposed trachyte182Holland, Dr., on Iceland228Horner, Mr., on a calcareo-animal substance201—— on fusibility of feldspar246Hubbard, Dr., on dikes247Humboldt on ejected fragments193—— on obsidian formations207,209—— on parapets round craters220—— on sphærulites210Hutton on amygdaloids176Hyalite in decomposed trachyte182Iceland, stratification of the circumferential hills228Islands, volcanic, distribution of248—— their elevation250Incrustation, on St. Paul’s rocks187Incrustations, calcareous, at Ascension199Jago, St.167James island234,237,242Jasper, origin of196Jonnès, M. Moreau de, on craters affected by wind189Juan Fernandez250Keilhau, M., on granite264Kicker Rock232King George’s sound259Labrador feldspar, ejected193Lakes at bases of volcanoes229Lamination of volcanic rocks209Land-shells, extinct, at St. Helena224Lanzarote, calcareous beds of223Lava, adhesion to sides of a gorge177—— feldspathic179—— with cells semi-amygdaloidal184Lavas, specific gravity of243,247Lava-streams blending together at St. Jago177—— composition of surface of208—— differences in the state of their surfaces244—— extreme thinness of238—— heaved up into hillocks at the Galapagos archipelago233—— their fluidity234,235—— with irregular hummocks at Ascension189Lead, separation from silver244Lesson, M., on craters at Ascension189Leucite234Lime, sulphate of, at Ascension200Lonsdale, Mr., on fossil-corals from Van Diemen’s land256Lot, St. Helena221Lyell, Mr., on craters of elevation227—— on embedded turtles’ eggs198—— on glossy coating to dikes216Macaulay, Dr., on calcareous casts at Madeira262MacCulloch, Dr., on an amygdaloid184—— on chlorophæite287—— on laminated pitchstone209Mackenzie, Sir G., on cavernous lava-streams233—— on glossy coatings to dikes216—— on obsidian streams208—— on stratification in Iceland228Madeira, calcareous casts at262Magazine, Nautical,—account of volcanic phenomena in the Atlantic226Marekanite206Mauritius, crater of elevation of184,227Mica, in rounded nodules168—— origin in metamorphic slate264—— radiating form of263Miller, Prof., on ejected Labrador feldspar193—— on quartz crystals in obsidian beds202Mitchell, Sir T., on bombs191—— on the Australian valleys254Mud streams at the Galapagos archipelago236Narborough island234Nelson, Lieut., on the Bermuda islands260,262New Caledonia248New Red sandstone, cross cleavage of253New South Wales251New Zealand259Nulliporæ (fossil), resembling concretions169Obsidian, absent at the Galapagos archipelago241—— bombs of191—— composition and origin of207,208—— crystals of feldspar sink in243—— its irruption from lofty craters246—— passage of beds into202—— specific gravity of243,246—— streams of208Olivine decomposed at St. Jago178—— at Van Diemen’s land257—— in the lavas at the Galapagos archipelago234Oolitic structure of recent calcareous beds at St. Helena223Otaheite183Oysters, extinction of258Panza islands, laminated trachyte of209Pattinson, Mr., on the separation of lead and silver244Paul’s, St., rocks of187Pearlstone206Peperino232Péron, M., on calcareous rocks of Australia262,263Phonolite, hills of179,181,221—— laminated210—— with more fusible hornblende246Pitchstone204—— dikes of209Plants, extinct257Plutonic rocks, separation of constituent parts of, by gravity246Porto Praya167Prevost, M. C., on rarity of great dislocations in volcanic islands217Prosperous hill, St. Helena218Pumice, absent at the Galapagos archipelago241—— laminated209,210,211Puy de Dome, trachyte of193Quail island, St. Jago168,170,173Quartz, crystals of, in beds alternating with obsidian202—— crystallised in sandstone252—— fusibility of246—— rock, mottled from metamorphic action with earthy matter170Red hill173Resin-like altered scoriæ171Rio de Janeiro, gneiss of252Robert, M., on strata of Iceland228Rogers, Professor, on curved lines of elevation249Salses, compared with tuff craters240Salt deposited by the sea200—— in volcanic strata201,215—— lakes of, in craters240Sandstone of Brazil265—— of the Cape of Good Hope265—— platforms of, in New South Wales252,265Schorl, radiating263Scrope, Mr. P., on laminated trachyte209,210,212—— on obsidian208—— on separation of trachyte and basalt244—— on silex in trachyte176—— on sphærulites210Seale, Mr., geognosy of St. Helena215—— on dikes226—— on embedded birds’ bones225Seale, on extinct shells of St. Helena224Sedgwick, Professor, on concretions206Septaria, in concretions in tuff198Serpulæ on upraised rocks185Seychelles248Shells, colour of, affected by light201—— from Van Diemen’s land256—— land, extinct, at St. Helena224—— particles of, drifted by the wind at St. Helena223Shelly matter deposited by the waves200Siau, M., on ripples254Signal Post Hill168,175,176Silica, deposited by steam182—— large proportion of, in obsidian206,208—— specific gravity of246Siliceous sinter196Smith, Dr. A., on junction of granite and clay-slate264Spallanzani on decomposed trachyte182Specific gravity of recent calcareous rocks and of limestone198—— of lavas245Sphærulites in glass and in silicified wood207—— in obsidian204,210Sowerby, Mr. G. B., on fossil-shells from Van Diemen’s land256—— from St. Jago169—— land-shells from St. Helena224St. Helena214—— crater of elevation of227St. Jago, crater of elevation of227—— effects of calcareous matter on lava231St. Paul’s rocks187,248Stokes, Mr., collections of sphærulites and of obsidians207,212Stony-top, Little218,222—— Great218Stratification of sandstone in New South Wales253,255Streams of obsidian208Stutchbury, Mr., on marine remains at Otaheite184Subsided space at Ascension192Tahiti183Talus, stratified, within tuff craters236Terceira182Tertiary deposit of St. Jago169Trachyte, absent at the Galapagos archipelago241—— at Ascension193—— at Terceira182—— decomposition of, by steam182—— its lamination200,210—— its separation from basalt244—— softened at Ascension194—— specific gravity of245—— with singular veins195Trap-dikes in the plutonic series247—— at King George’s sound259Travertin at Van Diemen’s land257Tropic-bird, now rare, at St. Helena225Tuff, craters of231,235,236—— their breached state240—— peculiar kind of231Turner, Mr., on the separation of molten metals244Tyerman and Bennett on marine remains at Huaheine184Valleys, gorge-like, at St. Helena225—— in New South Wales254—— in St. Jago180Van Diemen’s land256Veins in trachyte195—— of jasper195Vincent, Bory St., on bombs190Volcanic bombs189—— island in process of formation in the Atlantic226—— islands, their distribution248Wacke, its passage into lava183,257Wackes, argillaceous168,178Webster, Dr., on a basin-formed island237—— on gypsum at Ascension201White, Martin, on soundings254Wind, effects of, on the form of craters